Wet–cold preservation of West African yam (Dioscorea spp.) pollen

Abstract

Hermetic cold storage without previous drying (wet-cold storage) was experimented for the preservation of yam pollen grains. Pollens collected from white yam D. rotundata and a wild relative, D. praehensilis, were stored at k80, k20, 5, and 15 mC in sealed packs for 2 years. Pollen samples were drawn for in vitro germination tests after 100 and 700 days, and hand pollination was conducted after 365 and 730 days in storage. Pollen germination responses were not significantly different among the two species. Though pollen maintained germination capacity at all the storage temperature regimes, there was a significant loss in the viability of pollen stored at 5 and 15 mC after 100 days of storage. After 700 days in storage, pollens stored at 5 and 15 mC had lost germination capacity while there were no significant differences in the germination of fresh pollen and pollen frozen at k80 and k20 mC. Hand pollination with pollen of D. rotundata frozen at k80 mC for 365 days gave 69n5% fruit set and 50 % fruit set after 730 days in storage. From these results, the wet-freeze procedure appears promising to execute the establishment of pollen gene banks for yam breeding and for conservation of haploid gene pool of yams in base collections. A pollen storage protocol based on the procedure is recommended.

Optimized Protocol for In Vitro Pollen Germination in Yam (Dioscorea spp.)

“…Based on this study, the collected pollen should be used within 2 h for maximum results, as the viability is significantly reduced after 3-4 h. The screening of a large number of genotypes will be challenging as it takes 8-12 min for culturing pollen in a single Petri dish. Moreover, the recommended time for yam pollen collection is limited to the morning hours (8-11 a.m.) [8]. Rapid viability testing methods will, therefore, be necessary if high throughput phenotyping is desired for yam pollen.…”

“…Yam hybridization activities are often constrained by low, irregular and asynchronous flowering [5,6]. Selecting suitable pollen parents and preserving yam pollen for future use are potential means of managing these constraints [6,8]. However, implementing these practices in yam breeding programs requires a cost-effective and reliable pollen viability testing protocol, allowing the discrimination of genotypes for viability status and efficient monitoring of stored pollen.…”

“…Past studies on yam pollen used viability (germination) testing protocols from other crops without prior optimization [8][9][10], which led to a low uptake by the breeding programs. There is, therefore, a need to develop an optimized pollen viability testing method for yam to increase pollination efficiency, facilitate efficient monitoring of stored pollen and for genetic and physiological studies.…”

Root and Tuber Crops

“…Daniel et al (2002) have described conditions for preservation of yam pollen. The cold storage of pollen without pre-drying at -20 or -80 • C for periods as long as 2 years or more is an efficient means of conservation.…”

Exploring storage protocols for yam (Dioscorea spp.) pollen genebanking

“…and Daniel et al (2002) concluded that the maintenance of pollen grains of yam would be better at high moisture levels, arguing that the potential fertility of pollen grains is highest at shedding and at this stage, yam pollen grains are sticky (Ngu, 1991), indicating a high moisture content. This paper examines potential protocols for sustainable pollen storage based on results from various experiments conducted on the pollen grains of different West African yam genotypes.…”